1. FIELD OF THE INVENTION
This invention relates to a resistive controller, and more specifically to a membrane potentiometer, for use as a light dimmer or other voltage controlling device, that uses magnets to keep the membranes separated.
2. DESCRIPTION OF THE RELATED ART
Potentiometers are well known for controlling voltage selection in numerous types of applications in both home and industry. For example, these devices may be used in the control panels of such things as aircraft and aerospace applications, computers, arcade games, kitchen appliances, or lighting systems to name a few.
In the past, prior art Potentiometers for providing voltage selection have typically been operated using a mechanical wiper that is typically controlled by a knob or slider on a control panel. The wiper contacts a resistive element, which provides for voltage selection over a continuous range of voltages. The constant mechanical contact between the wiper and the resistive element tends to accelerate the wear and eventual failure of this type of potentiometer.
A more recently devised potentiometer uses a membrane comprising a continuous length of electrically resistive material, a corresponding continuous length to of electrically conductive material, which serves as a wiper, and an electrically insulating spacer which serves to simultaneously support and separate the resistive and conductive layers. Either one or both of the resistive and conductive materials are designed as flexible members so that they can be pressed together at any selected location along their length to bring them into electrical contact.
If a voltage is applied across the resistive material, a voltage gradient is established along the length of the material. Thus, touching either the top or bottom surface of the flexible member will cause the resistive and conductive materials to contact each other, producing a voltage output on the conductive material or wiper. The advantage of this device is that it minimizes wiper contact and reduces wear and yet provides a continuous range of output voltage levels.
A potentiometer membrane as described can be used to make a reliable and economical dimmer and/or switch for use with a light fixture. However, the flexible members must be kept separate, to prevent false readings, particularly in the middle of the member. In order to accomplish this, dielectric bumps are added to the member to keep portions of the member from sagging and touching each other. This problem becomes worse when the membrane potentiometer is desired to have a large area. Unfortunately, these dielectric bumps also cause portions of the resistors to become insulated which causes the output voltage from the resistor to have a nonlinear behavior which is undesirable.
It is desirable to have a large surface area membrane potentiometer with a linear output.
3. RELATED ART
Examples of patents that are related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:
U.S. Pat. No. 5,876,106 is an illuminated controller. PA1 U.S. Pat. No. 5,241,308 is a force sensitive touch panel. PA1 U.S. Pat. No. 5,228,562 is a membrane switch and fabrication method. PA1 U.S. Pat. No. 4,494,105 is a touch controlled circuit apparatus for voltage selection. PA1 U.S. Pat. No. 4,532,395 is a flexible touch switch plate. PA1 U.S. Pat. No. 3,968,467 is a touch controlled voltage-divider device.
The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicant's acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicant's claimed invention.